linux-kernel - [PATCH 13/13] perf record: Use sw counter only if hw pmu is not detected

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Message-Id: <1334178325-19148-14-git-send-email-acme@infradead.org>
Date:	Wed, 11 Apr 2012 18:05:25 -0300
From:	Arnaldo Carvalho de Melo <acme@...radead.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	linux-kernel@...r.kernel.org,
	Robert Richter <robert.richter@....com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 13/13] perf record: Use sw counter only if hw pmu is not detected

From: Robert Richter <robert.richter@....com>

Use cpu-clock-tick sw counter for cpu-cycles only if there is no hw
pmu available. This is the case if the syscall reports ENOENT. In
other cases (e.g. invalid attributes) we don't want the sw counter to
be used.

Cc: Ingo Molnar <mingo@...nel.org>
Link: http://lkml.kernel.org/r/1333643188-26895-5-git-send-email-robert.richter@amd.com
Signed-off-by: Robert Richter <robert.richter@....com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/builtin-record.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index be4e1ee..10b1f1f 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -245,7 +245,7 @@ try_again:
 			 * based cpu-clock-tick sw counter, which
 			 * is always available even if no PMU support:
 			 */
-			if (attr->type == PERF_TYPE_HARDWARE
+			if (err == ENOENT && attr->type == PERF_TYPE_HARDWARE
 					&& attr->config == PERF_COUNT_HW_CPU_CYCLES) {
 
 				if (verbose)
-- 
1.7.9.2.358.g22243

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